Responsiveness of the aging circadian clock to light

S. Benloucif*, K. Green, M. L'Hermite-Balériaux, S. Weintraub, L. F. Wolfe, P. C. Zee

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

38 Scopus citations


The present study assessed whether advances in sleep times and circadian phase in older adults might be due to decreased responsiveness of the aging circadian clock to light. Sixteen young (29.3 ± 5.6 years) and 14 older adults (67.1 ± 7.4 years) were exposed to 4 h of control dim (10 lux) or bright light (3500 lux) during the night. Phase shifts of the melatonin rhythm were assessed from the nights before and after the light exposure. Bright light delayed the melatonin midpoint in both young and older adults (p < 0.001). Phase delays for the older subjects were not significantly different from those of the young subjects for either the bright or dim light conditions. The magnitude of phase delays was correlated with both sleep offset and phase angle in the older, but not the younger subjects. The present results indicate that at light intensities commonly used in research as well as clinical practice older adults are able to phase delay to the same extent as younger subjects.

Original languageEnglish (US)
Pages (from-to)1870-1879
Number of pages10
JournalNeurobiology of Aging
Issue number12
StatePublished - Dec 2006


  • Advanced phase
  • Aging
  • Circadian
  • Light
  • Melatonin rhythm
  • Phase angle
  • Phase delay
  • Phase shift

ASJC Scopus subject areas

  • Neuroscience(all)
  • Aging
  • Clinical Neurology
  • Developmental Biology
  • Geriatrics and Gerontology

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